Section 1045 - Measurement Procedures for Vehicles in UseNoise from vehicles in use shall be measured as follows:
(a) Microphone Location. The sound level measuring microphone shall be in one of the following locations: (1) Primary Location. The microphone shall be located at a height not less than 0.6 m (2 ft), not more than 1.8 m (6 ft) above the plane of the roadway surface, and not less than 1.1 m (3.5 ft) above the surface upon which the microphone stands. The preferred microphone height on a flat surface is 1.2 m (4 ft).(2) Secondary Location. The microphone may be mounted on a boom affixed to the exterior of a passenger vehicle or the sound level meter with microphone attached may be held by a person sitting astride an open motorcycle.(A) When the microphone boom is used, the microphone shall be located 0.41 m ± 7.6 cm (16 in. ± 3 in.) above the highest point of the vehicle within an area bounded by the windshield, the tops of left and right front windows, and the rear of the driver's seat. The vehicle upon which the microphone is mounted shall be positioned so that its longitudinal axis is perpendicular to the center of the lane of travel. The height of the microphone above the plane of the roadway surface shall not exceed 2.4 m (8 ft). A correction factor of -2dB(A) shall be applied to the recorded sound level.(B) When the sound level meter with microphone attached is held by a person sitting astride an open motorcycle, the motorcycle shall be positioned parallel to the center of the lane of travel. The microphone shall be pointed toward the traffic and project beyond the windshield if the motorcycle is so equipped. The microphone shall be within the height requirements specified in preceding subsection (a)(1). A correction factor of -1dB(A) shall be applied to the recorded sound level.(b) Distance from Microphone to Target Point. The horizontal distance from the microphone to the microphone target point shall normally be 15.2 m (50 ft) but may range from 7.9 m (26 ft) to 30.2 m (99 ft) if the following correction factors are used: Distance from microphone to center of lane of travel | Sound level correction factor, dB(A)* |
7.9-8.8 m (26-29 ft) n........................... | .......................... -6 |
8.8-9.8 m (29-32 ft)........................... | .......................... -5 |
9.8-10.7 m (32-35 ft)........................... | .......................... -4 |
10.7-11.9 m (35-39 ft)........................... | .......................... -3 |
11.9-13.1 m (39-43 ft)........................... | .......................... -2 |
13.1-14.6 m (43-48 ft)........................... | .......................... -1 |
14.6-17.7 m (48-58 ft)........................... | .......................... 0 |
17.7-21.3 m (58-70 ft)........................... | .......................... +1 |
21.3-25.3 m (70-83 ft)........................... | .......................... +2 |
25.3-30.2 m (83-99 ft) **.......................... | .......................... +3 |
* If the distance from microphone to center of lane of travel falls on the midpoint between distance ranges given in the table, the larger correction factor shall be used.
** These distances are not applicable to measurements of heavy trucks with a gross vehicle weight rating (GVWR) of over 4,537 kg (10,000 lb) operated by motor carriers engaged in interstate commerce and governed by the Federal Bureau of Motor Carrier Safety regulations.
(c) Measuring Sites. Sites for measuring sound from vehicles in use shall meet the following requirements: (1) Standard Sites. As shown in Figure 1, standard measuring sites shall have the microphone 15.2 m (50 ft) from the lane of travel, be free of sound-reflecting surfaces within a 15.2 m (50 ft) radius of the microphone and of the microphone target point, and be approximately level. Click here to view image
(2) Modified Sites. Modified measuring sites shall meet the specifications shown in Figure 1, except the dimensions may range from 7.9 to 30.2 m (26 to 99 ft). The radii of the minimum clear area shall be the distance between the microphone and the microphone target point. Sound level readings taken at such sites shall be corrected as provided in preceding subsection (b). The site shall be free of large sound-reflecting objects, with the following exceptions:(A) The following objects may be anywhere within the site: 1. Small cylindrical objects such as fire hydrants or utility poles.3. Traffic railings of any type of construction except solid concrete barriers.4. Curbs having a vertical height of not more than 0.3 m (1 ft).5. Small bushes, shrubs, hedges, or trees.(B) The following objects may be within the measuring site but outside the triangular measuring area: 1. Any vertical surface (such as a billboard) regardless of size with a lower edge more than 4.6 m (15 ft) above the roadway surface.2. Any uniformly smooth, sloping surface rising away from the highway with a slope less than 45 deg above horizontal.3. Any surface rising away from the highway that is 45 deg or more and not more than 90 deg above horizontal if all points on the surface are more than 4.6 m (15 ft) above the roadway.4. Any object on the side of the vehicle path opposite the microphone with a width measured parallel to the vehicle path not exceeding 1.0 m (3.1 ft) regardless of height, and not slanting toward the roadway. If objects exceeding 1.0 m (3.1 ft) in width (such as parked vehicles) are on the side of the vehicle path opposite the microphone, a correction factor of -2 dB(A) shall be applied to the recorded sound level.(d) Moving Vehicles. Noise from vehicles in use shall be measured as the vehicle passes through the measuring site. Measurements shall be made under the conditions under which the vehicle is operating, regardless of vehicle load, grade, acceleration, or deceleration. (1) The traveled lane of the roadway within the measuring site shall be dry and paved with relatively smooth concrete or asphalt.(2) The traveled lane shall be free of holes or other defects that would cause a vehicle to emit irregular tire, body, or chassis impact noise and shall be free of significant areas of loose material such as sand or gravel.(3) The microphone target point shall not be within 61 m (200 ft) of a tunnel or underpass through which the vehicle travels.(4) The sound level must rise at least 6 dB(A) to the maximum level and fall at least 6 dB(A) below the maximum level as the vehicle passes to ensure that noise from other vehicles does not interfere with the sound of the vehicle being measured.(e) Stationary Heavy Motor Vehicles. Noise measurements of stationary in-use motor vehicles with a gross vehicle weight rating of more than 4,537 kg (10,000 lb) and equipped with an engine speed governor shall be made in accordance with the following procedures:(1) Vehicle Location: The vehicle shall be parked on a measuring site meeting the requirements of preceding subsection (c). The centerline of the vehicle shall be on the center of the lane of travel as shown in Figure 1. The vehicle shall be positioned so the exhaust system outlet is within 1.0 m (3.3 ft) of the microphone target point measured along the center of the lane of travel.(2) Auxiliary Equipment. Auxiliary equipment used only when the vehicle is stationary or operating at a speed of 8 km/h (5 mph) or less shall be turned off. Such equipment includes but is not limited to cranes, asphalt spreaders, ditch diggers, slurry pumps, auxiliary air compressors, welders, and trash compactors.(3) Engine Cooling Fans. If the engine cooling fan automatically disengages or reduces speed in response to reduced engine cooling loads, the engine shall be run at high idle, or any other speed the operator may choose, for sufficient time but not more than 10 min to permit the fan to operate at reduced speed during the noise test.(4) Engine Operation. With the transmission in neutral and the clutch engaged, the engine shall be rapidly accelerated from idle to its maximum governed speed with wide open throttle. After the engine speed has stabilized, the engine shall be returned to idle. This procedure shall be repeated until the maximum sound level readings are within 2 dB(A) of each other, disregarding unrelated peaks due to extraneous ambient sound.(5) Sound Level Measurement. The recorded sound level for the stationary vehicle shall be the numerical average of the highest 2 or more readings within 2 dB(A) of each other. This level shall not exceed 88 dB(A) on a measurement site with concrete, asphalt, packed dirt, gravel or similar reflective material for more than one-half the distance between the microphone and the microphone target point. The level shall not exceed 86 dB(A) on a measuring site with grass, other ground cover, or similar absorptive material for more than one-half the distance from the microphone target point.Cal. Code Regs. Tit. 13, § 1045
1. Repealer and new section filed 7-1-83; effective thirtieth day thereafter (Register 83, No. 27).
2. Amendment of subsection (a) filed 11-20-84; effective thirtieth day thereafter (Register 84, No. 47). Note: Authority cited and Reference: Sections 23130, 23130.5 and 27207, Vehicle Code.
1. Repealer and new section filed 7-1-83; effective thirtieth day thereafter (Register 83, No. 27).
2. Amendment of subsection (a) filed 11-20-84; effective thirtieth day thereafter (Register 84, No. 47).